Roof OK for loft conversion?

[Chris Johnstone]

I'm looking to extend up into my loft and am trying to work out initially what structural work will need doing. I want to put a long flat roof dormer at the back and velux's at the front. The house is 10 years old so is the 'W' shape style. I'm aware of steels needing to go in etc, I've just been up there to measure up and I've realised that the rafters aren't one long piece of wood, there is one (95mm x 35mm) that comes down from the ridge and one that comes up from the wall plate and they are joined in the middle with the metal plates. If I did go ahead and get it done, would these types of rafter need completely changing before taking the middle supports out or is it "get around-able"? Many thanks

 

[vinn]

Photos please?

 

[Doggit]

Almost certainly not get roundable. The middle supports are taking part of the strain of the rafters; without at least a perlin to support the rafters, you'd need larger but at least continuous rafters, but these could go alongside the existing ones.

Do you have a central wall that you can take the new joist to avoid needing steels.

But the caveat to all this will be the photos.

 

[noseall]

You have a truss rafter roof. None of that roof can be cut away. Not ideal for a loft conversion but doable with loads of cash and tons of steel and loads more wood. Basically you end up building a new roof and floor joists within the old one.

 

[Chris Johnstone]

Hi, thanks for the replies I'm going to attempt to put some pics up, I've tried to get the whole loft in but it wasn't happening! There is no central wall so will be party wall to party wall and there are currently 10 rafters (2 against one party wall then 8 spaced at 600mm to the other wall).

 

[noseall]

You will either need to remove the existing roof and build a new one or get a structural engineer/architect to design you a method of adapting what you have into what you want using steel, new joists and new rafters etc. Much of the existing stuff will be bolted to new stuff allowing you to remove the 'W' bits.

You do have a nice tall roof so the space looks good.

 

[Chris Johnstone]

Yeah, from joist to ridge board is near enough 4.5m so loads of room! I'd factored steels and new floor joists into my costings, so if it's just an extra 20 new rafters and some structural timber as an additional cost then that's not the end of the world, cheers

 

[Chris Johnstone]

Plus I have a separate roof pitch so additional loft with a lot smaller roof pitch as I have a walkway under our bedroom so the house is attached at the top but not the bottom, I'd like to see if I can knock a hole in the wall in the third picture and turn that space into a large "wardrobe / storage" space as the ceiling will be way to low to be a habitable room

 

[chappers]

If your building a dormer anyway, by far the cheapest method will be to re-cut the front roof

 

[catlad]

There was a thread a few years ago how a guy had his truss roof converted and in strong wind it made a lot of creaking noises and he wasn't happy at all
I would recommend you construct a new roof.

 

[freddiemercurystwin]

There's no real reason why a trussed roof cannot be converted, sure it may cost a little more but that's about the only difference.

 

[Doggit]

Going back to your opening post Chris, if you're intending to put a long dormer roof at the back, then you're basically rebuilding half the roof. You'll need a steel at the apex, but it should then be fairly simple to insert a new rafter alongside the old ones, put in a temporary perlin for support and then cut out the trusses. I suspect the job may not be as complicated as it might seem.

 

[^woody^]

so if it's just an extra 20 new rafters and some structural timber as an additional cost then that's not the end of the world, cheers

Don't forget the £15k for the scaffold canopy cover

 

[Doggit]

You'll need to discuss the job with an architect or a technician. They'll draw up the plans that you'll submit to a few builders, and if you can afford the quotes, then to Building control, and also to the Planning department if it's over permitted development. You'll need scaffolding front and back, but if it's done in the summer, then a canopy shouldn't be necessary, but the builder will include that in their price.

 

[^woody^]

but if it's done in the summer, then a canopy shouldn't be necessary

Yes, but the cost of moving the house to a sub-Saharan location for their summer, and back again, tends to be prohibitive.